Clogging dynamics for dripping irrigation systems using dairy effluent
Dinâmica de obstrução em sistemas de irrigação por gotejamento aplicando-se
efluente lactéo
DOI:10.34117/bjdv6n3-476
Recebimento dos originais: 10/02/2020 Aceitação para publicação: 30/03/2020
Ana Beatriz Alves de Araújo
Doutora em Manejo de Solo e Água pela Universidade Federal Rural do Semi-Árido Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: beatrizufersa@gmail.com
Salomão de Sousa Medeiros
Doutor em Recursos Hídricos e Ambientais pela Universidade Federal de Viçosa Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: salomao.medeiros@insa.gov.br
Francisco de Oliveira Mesquita
Doutor em Manejo de Solo e Água pela Universidade Federal Rural do Semi-Árido Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: francisco.mesquita@insa.gov.br
Pedro Henrique da Silva Oliveira
Doutor em Engenharia Química pela Universidade Federal do Rio Grande do Norte Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: pedro.oliveira@insa.gov.br
Emanoel Lima Martins
Doutor em Doutor em Ciência do Solo pela Universidade Federal da Paraíba Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: emanoel.martins@insa.gov.br
Neila Lidiany Ribeiro
Doutora em Zootecnia pela Universidade Federal da Paraíba Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: neilalr@hotmail.com
Ana Maria Gonçalves Duarte Mendonça
Doutora em Ciência e Engenharia de Materiais pela Universidade Federal de Campina Grande Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: ana.duartemendonca@gmail.com
João Paulo de Oliveira Simões
Mestre em Engenharia Civil e Ambiental Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: joao.simoes@insa.gov.br
Carlos Alberto Lins Cassimiro
Mestre em Ciências Agrárias pela Universidade Federal da Paraíba Instituição: Instituto Nacional do Semiárido – INSA
Endereço: Av. Francisco Lopes de Almeida, s/n - Serrotão, Campina Grande – PB, Brasil Email: carlos.cassimiro@insa.gov.br
ABSTRACT
The waterwater reuse in agriculture offers several social, economic and mainly environmental benefits. The fertigation process helps to minimize problems related to waste and environmental degradation when linked to the use of drip irrigation systems. However, it is a system that offers a high risk of obstruction due to the formation of colonies generated by the combination of physical, chemical and biological agents. The present work aimed to evaluate the alteration of indicators such as the Distribution Uniformity Coefficient (DUC) and Statistical Uniformity Coefficient (Su) of dripper units operating with diluted dairy effluent, detecting those most susceptible to the obstruction process. At the Soil Pollution and Degradation Laboratory, located in the Soil Sector of the Federal Rural University of the Semi-Arid - UFERSA, campus Mossoro/RN, the experiment was conducted by setting up an experimental bench with five drip units, whose performance was evaluated every 40h, until 200h of operation were completed. For this evaluation, characteristics such as ph, Electrical Conductivity (EC), Suspended Solids (SS), Dissolved Solids (DS), Calcium (Ca2+), Magnesium (Mg2
+), Total Iron (Fe), Total Magnesium (Mg2+) and Total Coliforms (TC). Drippers D1 and D5 were
more resistant to clogging, while emitters D2, D3 and D4 were more susceptible to this process. The coefficients studied showed classifications from good to excellent regarding the uniformity of distribution of the diluted dairy effluent.
Keywords: Wastewater, Uniformity of application, Clogging.
RESUMO
A reutilização da água na agricultura oferece vários benefícios sociais, econômicos e principalmente ambientais. O processo de fertirrigação ajuda a minimizar os problemas relacionados aos resíduos e à degradação ambiental quando ligados ao uso de sistemas de irrigação por gotejamento. No entanto, é um sistema que oferece um alto risco de obstrução devido à formação de colônias geradas pela combinação de agentes físicos, químicos e biológicos. O presente trabalho teve como objetivo avaliar a alteração de indicadores como o Coeficiente de Uniformidade de Distribuição (DUC) e o Coeficiente Estatístico de Uniformidade (Su) de unidades gotejadoras que operam com efluente lácteo diluído, detectando os mais suscetíveis ao processo de obstrução. No Laboratório de Poluição e Degradação do Solo, localizado no Setor de Solo da Universidade Federal Rural do Semiárido - UFERSA, campus Mossoró / RN, o experimento foi conduzido através da montagem de uma bancada experimental com cinco unidades de gotejamento, cujo desempenho foi avaliado a cada 40h, até 200h de operação. Para esta avaliação, características como ph, Condutividade Elétrica (CE), Sólidos Suspensos (SS), Sólidos Dissolvidos (DS), Cálcio (Ca2 +), Magnésio (Mg2 +), Ferro Total (Fe), Magnésio Total (Mg2 +) e Coliformes totais (CT). Os gotejadores D1 e D5 foram mais resistentes ao entupimento, enquanto os emissores D2, D3 e D4 foram mais suscetíveis a esse processo. Os coeficientes estudados mostraram classificações de boa a excelente em relação à uniformidade de distribuição do efluente lácteo diluído.
Palavras-chave: Águas residuais, Uniformidade de aplicação, Entupimento.
1 INTRODUCTION
In Brazil, milk is one of the most important products of agriculture, being essential for food supplying and in generating jobs and income for the population (EMBRAPA, 2016). Effluents, when discharged into bodies of water, correspond to a source of point pollution, that is, they reach the receiving body in a concentrated way in space. In particular, dairy effluents, where high organic load is a common feature. Because of this, when released into water bodies without proper treatment, they reduce the availability of dissolved oxygen, which can cause significant damage to the aquatic ecosystem (Silva, 2018).
The use of wastewater for irrigation is a viable alternative to supply water and nutrients to plants, in addition to contributing to the awareness of better use of water resources (Fischer Filho et. al., 2016). In this context, treated domestic sewage stands out for being rich in organic material, considered sustainable for application in agriculture especially due to the concentration of nutrients, such as nitrogen and phosphorus. (Schierano et al., 2017).
Another point to be considered is that the use of wastewater is an effective measure in controlling pollution, as it avoids the disposal of sewage in water bodies. (Oliveira et al., 2019). Localized irrigation can be used for the application of wastewater, given the high uniformity of application of the effluents and the low risk of contamination, in addition to operating at low pressures with high efficiency. Hence, maintaining the high uniformity of application of effluents in irrigation systems becomes essential for efficient irrigation in terms of the use of water resources and cost reduction. However, due to the presence of physical, chemical and biological agents in sewage effluent, drippers become susceptible to changes in flow and reduced uniformity of application (Fischer Filho et. Al., 2016).
Despite that, the drip irrigation system stands out as an option to reduce the impacts caused by the indiscriminate use of water in the agricultural sector, which currently accounts for 70% of its consumption; offering less environmental risk and greater application efficiency when compared to other irrigation systems. It is observed that the susceptibility to the obstruction problem does not appear uniformly in all dripper units, but according to the dripper characteristics and the quality of the effluent used.
The development of biofilm is due to the mutual influence between bacterial mucilages and organic and inorganic particles and this has been the fundamental factor for the incrustation of drippers that operate with wastewater (Fernandes et. Al., 2017).
Therefore, this article aims to assess the change in indicators such as the Distribution Uniformity Coefficient (DUC) and the Statistical Uniformity Coefficient (Su) of drip units operating with diluted dairy effluent, presenting those most sensitive to the clogging process.
2 MATERIAL AND METHODS
This work was carried out at the Federal Rural University of Semi-Árido (FURSA), at the Soil Pollution and Degradation Laboratory (LPDS), at the central Campus located in the county of Mossoro, state of Rio Grande do Norte (RN), under geographic coordinates 5º 12’12,31 ”south latitude, 37º 19’27,72” west longitude and altitude of 18 m above sea level.
In this region the climate received the classification Köppen type BSwh, being a dry climate, very hot and with rainy season in the summer being late for the fall. The climate of the region where the experimental area is inserted, according to the Köppen classification, is of the BSh type, being dry, very hot and with a rainy season in the summer, delaying to the autumn, with very irregular rainfall, with an annual average of 794 mm; annual average temperature of 26.5 °C; average relative humidity of 68.9%; average daily insolation of 7.83 hours and annual of 2,771.27 hours of sunlight and average wind speed of 0.84 m s-1, during a historical period of 30 years (Álvares et al., 2013). As can be seen in figure 1.
To carry out the tests, was assembled an experimental bench with useful area of 3.5 m2 was set up, being 1.4 m of wide by 2.5 m of long. For the recirculation of wastewater, was used a slope of 2.0% in the length direction. The same is composed of a plastic reservoir of 0.062 m3, a centrifugal motor pump of 0.5 hp, a screen filter openings with of'130 μm, two analog pressure gauges, two points for collecting effluent samples, a water meter of 1.5 m3 h-1, a main pipe with 32 mm PVC, a bypass pipe in PVC with 50 mm and five drip irrigation units, drawn at random. Each irrigation unit was composed of four 16 mm lateral lines of a dripper type. The illustrative scheme of the experimental bench can be seen in figure 2.
Figure 2. Illustrative scheme of the experimental bench mounted inside the UFERSA
In carrying out the experiment, were used two types of water: water of public supply, coming from the network of the Water Company and Sewers in Rio Grande do Norte and; the dairy wastewater from an enterprise located in the county of Mossoro (RN), under the geographical coordinates 5º11'44.65 ”S and 37º 18 '36.04” O, where, during the processing and sanitization of the facilities, it generates 35 m3 of effluent per day.
A portion of dairy effluent was diluted in two parts of public water supply (1:2), in order to reduce the viscosity of the crude residue and enabling its pumping. The emission lines, by where circulated the effluent, were composed by drippers, chosen due to their greater commercial market
demand, as can be seen in figure 3, whose characteristics, taken from the manufacturers' catalogs, are shown in Table 1.
Table 1. Drippers (D) used in experimental tests, highlighting the manufacturer (F),
self-compensating device (SCD), nominal flow (NF), flow coefficient (k), flow exponent that characterizes the flow regime (x), the filtering area (A), the length of the maze (L), manufacturing variation coefficient (MVC), recommended pressure range (P) and spacing between emitters (SBE).
Note: 1 - Nominal flow of the drippers at the operating pressure of 100 kPa; * information obtained from manufacturers' catalogs.
CNJ - anti-drain system; and ** information measured with the aid of a digital parking meter with an accuracy of 0.01 mm.
Figure 3. Image of drippers D1 (A), D2 (B), D3 (C), D4 (D) e D5 (E) used in the application of
dairy effluent diluted in public water supply
A B C
D E
During the experiment, was controlled the laboratory's room temperature so that the waste water was kept within the temperature range of 23ºC with variations of ± 3ºC, according
recommended by NBR ISO 9261 (Brazil, 2006), since temperatures between 20 and 30 ºC favor the formation of microbial mucus with high potential for obstruction for drippers (Pizarro Cabello, 1990). The irrigation units operated four hours by day, seven days a week until the operating time of 200 h was completed, operating at a working pressure of 100 kPa. In the methodology proposed by Mesquita et al., (2016), an operating time of 160 h was sufficient to provide dripper obstruction, operating with wastewater from the landfill leachate, and perform the assessment of its hydraulic performance.
The flow was measured in 24 drippers, from each irrigation unit, collecting the applied volume for three minutes. Capra & Scicolone (1998) and the NBR ISO 9261 (BRASIL, 2006), recommend, for the aforementioned collection time, the use of at least 16 drippers to assess the hydraulic performance of drip irrigation systems with clogging problems and, variations in flow between the drippers, in the initial operating time (0 h), in the range of ± 7%. The systems performance was evaluated every 40 h, using equations 1, 2 and 3:
𝐷𝑓 = 𝑉
1000 .𝑡 . 60 (1)
On what:
Df - Dripper flow (L h-1);
V - Volume of effluent collected (ml) e; t - Effluent collection time (min).
DUC = 100 . 𝑞25%
𝑞 (2)
On what:
DUC - Distribution Uniformity Coefficient (%);
q25% - Average value of the 25% lowest values of dripper flow rates (L h-1) e;
q - Average drip flow (L h-1).
𝑆𝑢 = 100 . (1 − 𝐹𝑉𝐶) (3)
On what:
Su - Statistical Uniformity Coefficient of effluent application (%) e;
FVC - Flow Variation Coefficient (%).
The values of DUC and Su obtained in the drip units were analyzed using the criteria established by Mantovani (2001), who proposed the following classification for the DUC: greater than 84% excellent, between 68 and 84% good, between 52 and 68 % reasonable, between 36 and 52% bad and, less than 36% unacceptable e; Su: between 90 and 100% excellent, between 80 and
90% good, between 70 and 80% reasonable, between 60 and 70% bad and, less than 60% unacceptable.
In Table 2, shows the values corresponding to the physical-chemical and microbiological analyzes carried out for the dairy wastewater diluted in public water supply (in the proportion of 1:2). To this end, the recommendations of the Standard Methods for the Examination of Water and Wastewater (RICE et al., 2012), described below, were followed.
Table 2. Physico-chemical and microbiological characteristics of a part of dairy effluent diluted in
two parts of public water supply with respective mean and standard deviation.
Characteristics pH CE SS SD Ca2+ Mg2+ Fe Mn CT - dS m-1 mg L-1 mmol c L-1 mg L-1 NMP 100 mL-1* Mean 7.67 1.24 393 929 0.87 1.08 0.20 0.07 3.77x105 Standard deviation 0.23 0.06 177 196 0.33 0.69 0.08 0.01 1.84
Note:2 Hydrogen potential (Hp), Electric conductivity (EC), Suspended Solids (SS), Dissolved Solids (DS), Calcium (Ca2+),
Magnesium (Mg2+), Total iron (T.Fe2+), Total manganese (T.Mn2+), Total Coliforms (TC) and Most Likely Number (MLN).
The physical analyzes, carried at the Soil, Water and Plant Analysis Laboratory (SWPA), of Center for Agricultural Sciences (CAS), at FURSA, understood the determination of Dissolved Solids (DS) obtained by the difference between the concentrations of Total Solids (TS) (by gravimetric method) and Suspended Solids (SS) by gravimetric method with the use of glass fiber membranes (0.45 μm pore diameter); of hydrogen potential (Hp) with bench diameter and; Electric conductivity (EC) by bench conductivity meter.
In the chemical analyzes, carried in the Laboratories of Organic Matter and Residues and Atomic Absorption Spectrometry, of the Soil Department (SD), from the Federal University of Viçosa (FUV), were obtained the concentrations of total iron (Fe2+) and total manganese (Mn2+) by
atomic absorption spectrophotometry (AAS). They obtained also, Calcium analysis (Ca2+) and
Magnesium (Mg2+) by the titrometric method, in Soil, Water and Plant Analysis laboratory (SWPA) and from FURSA.
In the microbiological analyzes carried out at the Environmental Sanitation Laboratory (ESL) of the Engineering Center (EC) at the FURSA, the population levels of Total Coliforms (TC) were quantified, according to the recommendations of the Standard Methods for Examination of Water and Wastewater (Rice, et al., 2012).
The wastewater quality data of dairy were analyzed through descriptive statistics using mean and standard deviation.
3 RESULTS AND DISCUSSION
The irrigation units subjected to the service pressure of 100 kPa, during the initial operating period (0 h) and 80 h, showed values for the Distribution Uniformity Coefficient (DUC) between 98 and 90%, with the exception of D2 that at 80 h showed a percentage of 89%. Between 120 and 200
h, only the D4 drippers (with the exception of the 160 h in which it showed 80%), D1 and D5 remained with their coefficients above 90%, varying between 91 and 97%, while the D3 and D2 showed values between 82 and 89%, as can be seen in Figure 4.
Figure 4. Average values of the Distribution Uniformity Coefficient (DUC-%) of the irrigation
units for the drip factor within each level of operating time and service pressure of 100 kPa
Merriam and Keller (1978) presented the following general criteria for interpreting DUC values, for systems that have been in operation for one or more years: greater than 90%, excellent; between 80 and 90%, good; 70 and 80%, regular; less than 70%, bad.
Thus, analyzing the figure above, it was found that the drippers D1 and D5 (greater than 90%) had an excellent classification, while at 160 h the drippers D3 (with 83%) and D4 (80%), as well as the D2 (82%) at 200 h, were classified as good.
Mesquita (2016), working with landfill leachate effluent in the performance of dripping units in the operating time from 0 h to 160 h and at the service pressure of 100 kPa found, at the beginning of the experiment (0 h), DUC values of the units irrigation above 90%, being classified by Merriam & Keller (1978) as excellent (DUC> 90%). In the 160 h evaluation time, the DUC of the D1 dripper irrigation unit was 78% classified as good (70% <DUC <80%); in irrigation units with drippers D2, D3 and D4 the DUC values were 96, 98 and 97%, respectively, classified as excellent (DUC> 90%) by Merriam & Keller (1978). Franco (2015), in his experiment with swine wastewater, also obtained uniformity variation values classified as excellent, with percentages above 90%.
Vale (2019) also found the average CUD values greater than 90%, being classified as excellent in the initial and final operation times, except when submitted to the T5 treatment, which obtained a regular classification (between 70 and 80%) according to Merriam & Keller (1978) at 160 h operating time and service pressure maintained at 100 kPa.
The obstruction of emitters is pointed out as one of the greatest maintenance difficulties in microirrigation, being entirely linked to the quality of irrigation water (Perboni, 2018), an act that directly affects the uniformity of application and, consequently, the efficiency of the system through the presence and, consequent, accumulation of inorganic particles in suspension, organic materials, dissolved solids, algae and other microorganisms of chemical and biological nature (Cunha, 2017).
However, as shown in the classification, the system, during the experimental period, did not present a great compromise in its efficiency, since it was classified as good and excellent, an act probably given by not using the pure dairy effluent, but diluted in water. Supply, in the proportion of 1: 2, which led to the development of a relatively well developed irrigation system in which a better range of application uniformities was allowed.
The irrigation units subjected to the service pressure of 100 kPa, in the initial operating times and 120 h, showed values of the Statistical Uniformity Coefficient (Us) between 98 and 90%, with the exception of D3 which at 120 h showed a percentage approximately 85%. Between 160 and 200 h, only the D4 drippers (with the exception of the 160 h in which it showed itself with approximately 83%), D1 and D5 remained with their coefficients above 90% - varying between 94 and 96%, while the D3 and D2 showed values between 87 and 88% as can be seen in Figure 5.
Figure 5. Mean values of the Statistical Uniformity Coefficient (Us) of the irrigation units for the
According to the classification proposed by Mantovani (2001), Us presents itself with the following values: between 90 and 100% excellent, between 80 and 90% good, between 70 and 80% reasonable, between 60 and 70% poor and, lower that 60% unacceptable. Thus, analyzing the figure above, it was found that the D1 and D5 drippers had an excellent classification, while at 160 h the D4 dripper (with approximately 83%), the D2 from 160 to 200 h (with approximately 88 and 89 h) %, respectively) and D3 from 120 to 200 h (with 85 and 88%, respectively), were classified as good.
Pereira et. al., (2016), evaluating the efficiency of water application in a pasture sprinkler irrigation system, found a Statistical Coefficient value of 75.41%, being classified as reasonable by (Mantovani, 2001), coefficients above 75% are accepted at commercial level. Franco (2015), in his experiment with swine wastewater, also maintained the efficiency ranges above 90%, an act that did not allow the compromise by partial obstructions.
4 CONCLUSION
The evaluated emitters are among the classification levels from excellent to good for the Distribution Uniformity Coefficient (CUD) and Statistical Uniformity Coefficient (Us).
The G1 and G5 drippers, operating at 100 kPa operating pressure, are the most recommended for the application of dairy waste water diluted in public water supply in the proportion of 1: 2, since they were more resistant to the development of obstructions. While emitters the G2, G3 and G4 were the ones most susceptible to this process.
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